Certain platinum complexes are active against tumors and this discovery has spawned a renewed interest in metal complexes in general as a source of anti-cancer agents. Cisplatin, cis-[Pt(NH.sub.3).sub.2 Cl.sub.2 ], for example, has been singularly successful in bringing about a regression of testicular and ovarian tumors and, as a result, other platinum derivatives have been investigated for anti-tumor activity.
These developments have led to the exploitation of structure-activity relationships, including the synthesis of various palladium analogs; however, most palladium analogs have failed to show any discernable activity, and the activity which has been observed is of a very low order. Speculation has it that the palladium(II) amine complexes are extremely reactive and this liability causes them to react with other molecules in vivo prior to reaching the cancer which is sought to be treated (M. J. Cleare and J. D. Hoeschele; Bioinorganic Chemistry, Vol. 2: page 187 (1973); and M. J. Cleare; Coordination Chemistry Reviews, Vol. 12: page 349 (1973)). Accordingly, it has been impossible heretofore to develop a class of palladium compounds which parallel the known platinum-containing anti-tumor agents.